They have similarities - they're designed to operate enclosed by a hostile medium - but also crucial differences - a submarine is very hard to detect; a space-ship is easy to detect except when there's a large chunk of rock (or giant explosion) in the way - just look for the object at room temperature...

Flumble wrote:One does not simply combine two Greek words to form an English one.

That's exactly how English words are formed. We don't "borrow" words from other languages, we track them down in dark alleys, hit them from behind, and go through their pockets for loose grammar.

Jose

Order of the Sillies, Honoris Causam - bestowed by charlie_grumbles on NP 859 * OTTscar winner: Wordsmith - bestowed by yappobiscuts and the OTT on NP 1832 * Ecclesiastical Calendar of the Order of the Holy Contradiction * Please help addams if you can. She needs all of us.

Flumble wrote:One does not simply combine two Greek words to form an English one.

That's exactly how English words are formed. We don't "borrow" words from other languages, we track them down in dark alleys, hit them from behind, and go through their pockets for loose grammar.

I'm sorry, I forgot to mention this must be done by combining a Greek and a Latin word. That's why I continued with chaos and vās.

In reality, there are a few Greek-Greek words, but AFAIK most of the classic combinations are a mix of Greek and Latin, just to fuck with us.

Oh. In that case, well done. Axios!

Jose

Order of the Sillies, Honoris Causam - bestowed by charlie_grumbles on NP 859 * OTTscar winner: Wordsmith - bestowed by yappobiscuts and the OTT on NP 1832 * Ecclesiastical Calendar of the Order of the Holy Contradiction * Please help addams if you can. She needs all of us.

With the reference to Sir Terry Pratchett, it occurs to me that the Discworld character Leonard da Quirm would almost certainly have designed a Jupiter subaerine at some point, but would not see any possible use for it, and would (probably) never build it.

There's a point in Jupiter's atmosphere where the pressure is equal to a little more than an Earth atmosphere—which is the pressure a submarine is used to—but the air there is barely a tenth as dense as ours.

Seeing as we're using submarines as a reference and not people, wouldn't it make more sense to use the maximum operating depth pressure as a reference height on Jupiter than 1 atm?

Submarines are used to an order of magnitude or so above "a little more than Earth's atmosphere". Pressure under water rises about 1 atm every 10m. The bottom of any large ship is under 2 atm or more when floating on the surface, and even non-classified military submarine depths are at 10 atm or more. Trieste took over 1k atm. Subs have to account for buoyancy falling as the hull compresses - even before note 1 effects. Sea water is a little more dense due to pressure at those depths, but the effects of temperature, salinity, and hull compression are much larger.

Which does not alter the basic answer. It is just surprising how much more pressure a little water exerts compared to a lot of air.

If you set up an osmotic membrane with sea water on one side and fresh water on the other, if enough pressure is applied on the sea-water side, fresh water will be pushed through from the sea water side. You could do this in a static setup, with an air-filled vertical tube in the ocean, with the membrane at the bottom end. If the tube is long enough that the pressure differential at the bottom end between the sea water and the air is great enough, fresh water will be pushed through until the osmotic pressure balances the sea water pressure vs. fresh water pressure + air pressure.

The fun thing is that sea water is denser than fresh water.

So if you lengthen the tube, with the membrane end still lower down, the equilibrium level of the fresh water will be a bit higher than it was. If you make the tube long enough, the equilibrium level of the fresh water will be at the top of the tube: the pressure differential between the slightly-lower-density column of water will balance the osmotic pressure and the slightly-higher-density sea water.

And if the tube is slightly longer still, it can raise the equilibrium level of the fresh water to above the level of the sea water.

Unfortunately, the required length of the tube is greater than the greatest depth of the ocean. It's been a while since I ran the numbers, and there are factors that I don't know enough about; I don't recall if the difference is "somewhat" or "much" more than that depth. And it's not practical, because the membrane would get fouled by crud, probably fairly quickly.

I know it looks like a perpetual-motion machine. So far as I can figure it out, it's driven by the "falling" ocean salts. The temperature change of any work done isn't relevant; the ocean would be a heat sink. And it's not truly perpetual; there would be increasing salinity at the bottom end, not taking into account mixing caused by a variety of factors.

Was it in one of these forum threads that there was a discussion recently of blimp-like research stations in Venus' atmosphere, or was that an actual article from some (dare I say it) space cadet?

Bit late to the party here, but the Soviets have twice flown instrumented balloons in the Venus atmosphere:http://mentallandscape.com/V_Vega.htmThey each flew for nearly two full days before running out of battery.

I get that air, or whatever mix that passes for air is used in Jupiter, is not water, and that ships might sink to the very bottom, but with subs being more or less perfectly enclosed, wouldn't they function like very heavy blimps? Which do float in air?

This obviously assumes that the atmosphere gets to the required density, but I'm not seeing why that wouldn't work like any other balloon would.

Flumble wrote:One does not simply combine two Greek words to form an English one. Either χαος has to become chaos or σκαφη has to become vās.Chaoscaphe does have a ring to it.

That said, if I were on a sinking boat, I'd totally say "This is a Chaoscaphe!"

I came here to make sure I didn't miss footnote four, but now I just want to say that I'm pronouncing this word as "chaos coffee." Which sounds like the sort of thing the captain of a submarine sinking in Jupiter might drink.

peregrine7 wrote:I get that air, or whatever mix that passes for air is used in Jupiter, is not water, and that ships might sink to the very bottom, but with subs being more or less perfectly enclosed, wouldn't they function like very heavy blimps? Which do float in air?

This obviously assumes that the atmosphere gets to the required density, but I'm not seeing why that wouldn't work like any other balloon would.

Um, I think Randal answered than in the second sentence of the piece: " At the point in Jupiter's atmosphere where the density is high enough for a submarine to float, the pressure is high enough to crush the submarine,[1] and the temperature is high enough to melt it.".Implying that the density does indeed become greater than that of an intact submarine, but a conventional steel submarine would not remain intact. On the other hand if you have a plentiful supply of unobtainum and a really good air conditioner....

Trieste made it over 1000 atmospheres in the trench right? And air is only what 750 times less dense than water? Seems to just be a heat issue and that can surely be engineered away right? Or am I missing something big?

Eshru wrote:Trieste made it over 1000 atmospheres in the trench right? And air is only what 750 times less dense than water? Seems to just be a heat issue and that can surely be engineered away right? Or am I missing something big?

Add an extra factor of fifteen to account for the difference in molecular weight between hydrogen and Earth air.